Karen L. Erickson

Chamigrane metabolites from a Jamaican variety of Laurencia obtusa

Abstract Two new sesquiterpenoid metabolites have been characterized from a Jamaican variety of the marine alga Laurencia obtusa. These are 2-chloro-3-hydroxy-α-chamigren-9-one, with an unusual cis-relationship of the heteroatoms at the 2,3-positions, and its intramolecular conjugate addition derivative possessing a cineole moiety fused to a cyclohexane ring.

Stylopeptide 2, a proline-rich cyclodecapeptide from the sponge Stylotella sp.

A new proline-rich cyclodecapeptide, designated stylopeptide 2, has been isolated from a cytotoxic extract of the Papua New Guinea marine sponge Stylotella sp. and found to correspond to structure 1. The structural assignment was based on HRMS collision-induced dissociation tandem mass spectrometry (CID MS/MS), NMR spectroscopic data, and amino acid analysis, which led to assignment of the absolute configuration.

Lauroxolanes from the marine alga Laurencia majuscula

Abstract Enyne 1 was isolated from the marine red alga Laurencia majuscula , and its structure was elucidated by spectroscopic means. 1 is the first 2,2′- bis -tetrahydrofuran lauroxane to be found as a Laurencia metabolite.

Branched chain mono-glycerol ethers from a taiwanese marine sponge of the genus Aaptos

3-(13-Methylhexadecyloxy)-1,2-(S)-propanediol (6) and 3-(15-methyloctadecyloxy)-1,2-(S)-propanediol (7) were isolated from an Aaptos species of marine sponge from Taiwanese waters and characterized by spectroscopic methods. Homolog 6 was independently synthesized.

Synthesis and cytotoxicity of a salicylihalamide A analogue.

The synthesis of a simple analogue of salicylihalamide A with a truncated lactone ring (+/- 2) was achieved in 10 steps. Its cytotoxicity profile in the NCI 60-cell-line human tumor assay differed significantly from that of salicylihalamide A in both level and specificity.

Carbanionic Rearrangements of Halomethylenecyclobutanes. Stereochemistry of the Migrating Group

The unusual base-induced ring-enlargement of halomethylenecyclobutanes to 1-halocyclopentenes was examined with unsymmetrical and (13)C-labeled substrates to study regio- and stereochemical characteristics. Migration of a ring carbon atom (single migration) or simultaneous migration of a ring carbon atom and the halide (double migration) gives the ring-enlarged products. (13)C-labeling experiments established that both rearrangements occur with retention of configuration at the migrating center. These systems are suggested as models for the Fritsch-Buttenberg-Wiechell (FBW) rearrangement.

Rottnestol, a new hemiketal from the sponge Haliclona sp.

Summary Rottnestol, a new hemiketal, was isolated from an Australian collection of the marine sponge Haliclona sp. Its structure was deduced as 3 from 1H, 13C, COSY, HMQC, HMBC and nOe NMR studies. Hemiketal 3 was readily converted to its epimer, 4, and the methyl ketal of 4.

Acid-catalyzed oxygen-transfer reactions of ortho-alkenyldimethylbenzylamine oxides

Several ortho-alkenyldimethylbenzylamine oxides were found to rearrange in strong acid media to mixtures of aminophthalans and conjugated aminoketones

Models for uleine-alkaloid biogenesis

Abstract Possible mechanisms by which the C2-unit of the tryptamine bridge of condylocarpine-type alkaloids can be lost to give the uleine skeleton are considered. A terminally-oxidized β-C2 substituent on an α-methyleneindoline system could not be cleaved, but a β-C3 acid unit fragmented readily.

Reassignment of stereochemistry of the 3‐ethoxy‐2‐methyl‐2‐vinylcyclobutanones

The syn and anti stereoisomers of 3‐ethoxy‐2‐methyl‐2‐vinylcyclobutanone were prepared. Reinterpretation of the literature 13C spectra led to an inversion of the original structure assignments. Confirmation of relative stereochemistry was provided by NOE difference experiments. Copyright